best way to remove solder flux?

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mightyohm
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best way to remove solder flux?

Postby mightyohm » Tue Apr 07, 2009 1:37 pm

I usually use Isopropyl Alcohol (90+%) from the drugstore, but even after scrubbing I get a slight white residue that is really difficult to remove. The best stuff I have found is MG Chemicals Heavy Duty Flux Remover, but it smells terrible and is probably horrible for me and the environment.

What is everyone else using?

Tony
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Re: best way to remove solder flux?

Postby Tony » Tue Apr 07, 2009 1:49 pm

I usually use IPA with a toothbrush and pour copious amounts on, scrub, and make a huge mess. Obviously the purer the IPA the better. I think there are different grades available. I would say stay away from stronger solvents. And be careful with potentiometers and variable caps. They have a way of trapping stuff and then years down the road failing.

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Re: best way to remove solder flux?

Postby mightyohm » Sat Aug 01, 2009 6:31 pm

Since my original post, I have found that TechSpray G3 series flux remover works really well, but will melt some plastics. It is truly nasty stuff, I wear gloves and goggles when using it.

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CircuitGizmos
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Re: best way to remove solder flux?

Postby CircuitGizmos » Thu Nov 12, 2009 3:39 pm

Jeff:

Mix IPA 50/50 with common blue Windex. The ammonia in the Windex removes the salty white residue.

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Re: best way to remove solder flux?

Postby mightyohm » Thu Nov 12, 2009 4:44 pm

Seriously?! I will have to try this out! Thanks for the tip!

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CircuitGizmos
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Re: best way to remove solder flux?

Postby CircuitGizmos » Thu Nov 12, 2009 5:11 pm

mightyohm wrote:Seriously?! I will have to try this out! Thanks for the tip!


Yeah seriously. I talked to a chemist that worked in an assembled PCB manufacturing facility and he confirmed it. We did some testing and ultimately I combined $5 worth of Target (store) products. Mind you we didn't test with all flux types, but I've personally used this "secret recipe" with 3 or 4 different soldering fluxes with complete success. Not just hand-built projects, but instituted as the cleaner for a commercial endeavor.

You can soak a board in this, scrub with a toothbrush, rinse with hot water. Additional cool rinse with distilled water, if need be.

valgamaa
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Re: best way to remove solder flux?

Postby valgamaa » Tue Feb 15, 2011 6:32 am

I use a 50:50 mixture of IPA and domestic bleach, which works well for me. It is the same principle as the Windex mixture, but easier to obtain (at least in the UK). The board needs to soak for a few minutes, then rinsed under a tap. Of course this needs to be done before fitting pots, trimmers and any other parts that need a lubricant.

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Re: best way to remove solder flux?

Postby mightyohm » Wed Feb 16, 2011 8:02 pm

Thanks for the tip on bleach. I will experiment with these combinations and report back.

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Re: best way to remove solder flux?

Postby mnphysicist » Wed Mar 02, 2011 7:52 pm

Be aware that solder mask issues, flux type, and process temps can change properties enough that one type of cleaning may work fine, and then on another run of boards it wont. In the old days, we'd plot a grid array with terminations on the carrier part of the pcb assembly just for periodically testing the cleaning process. My personal favorite was trichlor, but short of Uncle's exemption for space and mil, its no longer available.

For homebrew, I generally use acetone if the solder mask will stand up to it, otherwise isopropyl for most non-aqueous fluxes. For aqueous fluxes, Dawn dishwashing detergent and really hot water work pretty well... even better if you can run your boards through a dishwasher (a dedicated one, not the one in your kitchen). For no-clean... its a mess. No clean flux should only be used on the most insensitive circuits, or ones where long life span under extended temperatures is not a design criteria.

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Re: best way to remove solder flux?

Postby mightyohm » Wed Mar 02, 2011 8:16 pm

I tried the Windex/isopropanol cocktail over the weekend, and while it did seem to reduce amount of white deposits left on the boards, it wasn't nearly aggressive enough to clean flux out from under the leads of some fine pitched ICs on my board.

I ended up using a commercial heavy duty flux remover (what was left of a can of TechSpray G3) and that was the only thing I could find that would touch the flux deposits under the IC leads. 99.9% isopropanol just turned the flux into a white mess.

Ultimately I think I need to change flux from RMA to one with lower solids content or alter my assembly method to reduce the amount of extra flux I am using.

mnphysicist - Perhaps I should try switching to water soluble flux and see what happens. I hate exposing my boards to water (they take a long time to dry, for one), but I would like to use less nasty solvents for cleanup.